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  1. #1
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    Default Test & Tag Machine Calibration

    Sort of off topic for this forum, but I know there are members here who have experience with calibration who might be able to shed some light on this for me.

    I had the test & tag machine from work calibrated today. I'm good at maths, but I'm confused by the report. There are uncertainty numbers in the mid-20s for some tests. They explained to me that this is the error of their calibration machine, which is deducted from the error of the machine under test to get the net error of the machine under test. They said they had just had their testing machine calibrated. I find it odd that a machine designed for calibrating other machines could have uncertainty figures as high as 29%.

    My scepticism wasn't helped by the fact that the person who did the test wasn't the person whose name was on the report as the tester. Apparently the person who did the test is new and used the login of an existing employee. Pretty unprofessional if you ask me.

    Can anyone shed any light of the dark arts of machine calibration?
    Chris

  2. #2
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    Default

    Here's the report.
    Attached Files Attached Files
    Chris

  3. #3
    BobL is online now Member: Blue and white apron brigade
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    I've seen this sort of thing a few times especially amongst students and its a classic confusion between "Difference" and "uncertainty".
    Metrologists (not meteorologist) would shake their heads in shame over this.

    The difference between a measure reading and a standard or acceptable measurement reading is NOT an "uncertainty" or "error" - it's just a "difference"

    The column headed "Test Uncertainty" should be more correctly expressed as a "Test difference".

  4. #4
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    I agree with what Bob has said, but would go further and say that test report is a waste of paper. The normal way of doing these things is to quote a result of say 32.5mm with an uncertainty of 0.05mm. An uncertainty as a percentage means nothing. Uncertainty represents a statistical band of error, where you are qualifying the result that is obtained by saying how much that may vary due to factors that may influence the measurement.
    I am not sure about the validity of quoting a reference value to 4 decimals and directly comparing that to a measured value to 2 - while mathematically valid, it does not sit right. In addition, mid upper left there is a section with 'required uncertainty' values. Required current values are stated to be 5%, but the object under test has values of greater than this and is still given a pass. Either the person writing the report has no idea or the report is not clear enough in what that applies to to be relied on.

    If it were me getting this report, I would be looking for a new test house. Unclear reports, passes that seem to be fails, signing with someone else's name... At the very least you should be raising this with their management. See if you can find a test house that is (preferably) NATA accreditted or runs an ISO quality system, as when I read that report the word 'cowboy' springs to mind.

    The problem is that if you use that piece of equipment to test, pass something and there is later an incident where someone is injured, a report like that would not help in your (legal) defence. While you could rely on the "we went to them because they are experts" line, the problems with the report are the sort of thing that the counter claim would be "but anybody with the appropriate background looking at that report would counclude there are errors in it". It's about risk.

    Michael

  5. #5
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    Thanks Gents.

    I agree that test uncertainty as a percentage just doesn't make sense for this type of report. I had an inkling the test was worthless. The first person I queried about the results was a bloke in his 70s who could have been the owner. He had absolutely no idea what the report was saying.

    I will be contacting them today for an explanation.
    Chris

  6. #6
    BobL is online now Member: Blue and white apron brigade
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    Quote Originally Posted by jack620 View Post
    Thanks Gents.

    I agree that test uncertainty as a percentage just doesn't make sense for this type of report. I had an inkling the test was worthless. The first person I queried about the results was a bloke in his 70s who could have been the owner. He had absolutely no idea what the report was saying.

    I will be contacting them today for an explanation.
    When T&T first came in to or work requirements our department at Uni selected a techo who was going to do the T&T and he was sent along to training. Because the uni had several dozen techs who were going to be T&Ting they organised for a trainer to come to Uni and I went along to the first session meet the trainer and suss it all out. Within a couple of minutes I could see the trainer only had a very basic understanding of electricity as all he did was read from prepared notes and powerpoint slides and handed out forms produced by someone else. He was very vague on a number of questions posed to him and some he could not answer at all. A couple of the senior techos even left the training early in disgust.

    The documentation requirements was onerous, confusing and in some cases plain wrong, and was clearly 90% covering. Several of us went through the paperwork with the Uni's OHS people, who also knew stuff all about electricity. I taught basic electricity to the undergraduates from the OHS degree course and if they were anything to go by, lucky we have sparkies. Our main concern was taking our skilled techos away from their regular duties to deal with this nonsense. We offered to correct the forms and streamline the process but Uni legal said we had to do it using the provided paperwork. In the end each faculty ended up employing several full time people to deal with this. The fella we hired for our area was a very friendly down to earth sparky who was licensed to fix and minor problems on the spot, but he nearly left over the paperwork requirements. Our fella did a number of useful things like find and chuck out quite a bit of suss gear - some of which I manage to pick up and fix so it was not all bad.

    I believe the whole T&T thing has been been significantly streamlined and automated since I left.

  7. #7
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    Quote Originally Posted by BobL View Post
    Within a couple of minutes I could see the trainer only had a very basic understanding of electricity...
    Same with the bloke who ran my course.

    Quote Originally Posted by BobL View Post
    I believe the whole T&T thing has been been significantly streamlined and automated since I left.
    It has. The Australian Standard is pretty clear and the machines do most of the work for you.

    Looking closer at the report- If you look at the first line the difference between the "test range" of 0.5453 and "test reading" of 0.58 is 6.4% as indicated. T&T machines are required to be accurate to within 5%. I assume that's what the 0.05% (sic) refers to (it should read either 0.05 or 5%, not 0.05%). So that would make that test a FAIL, as 6.4%>5%. However they then apply the "test uncertainty" of 6.5% which magically brings the result back within range and therefore a PASS.

    Similarly, the RCD trip current test has an error of 29% to which they apply a 29.1% correction resulting in a PASS. The whole thing seems dodgy. It's like they are just making up corrections to ensure a PASS. Perhaps they figure if they fail the device the client won't pay, or won't give them any more work?

    I've tried ringing them today, but they aren't answering. FWIW, this is not some backyard operation. It's a big company with offices in nearly every State. I've told my accounts department not to pay the bill until I'm satisfied the report isn't a complete fudge.
    Chris

  8. #8
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    So I got a call from a very aggressive young female manager who was unhappy that I had questioned her report (she was quite loopy actually). She reckons the uncertainty figure represents the uncertainty of the whole test setup (cables, etc). I don't buy it. If that's the case, why does it vary so much between tests? After our conversation I don't believe they are dodgy, I just think they are out of their depth.

    After changing her story a couple of times about the whole process, she told me not to pay the bill and never return. Your wish is my command! Anyone know a competent electrical calibration facility in Melbourne (don't say IPD!).
    Chris

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    Celemetrix, but it won’t be cheap.
    https://www.celemetrix.com.au/

  10. #10
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    Brilliant! Thanks a million. I’m surprised they didn’t come up in my Google search. At least they are NATA accredited which the other mob apparently aren’t.
    Chris

  11. #11
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    This is Australia in 2020. You no longer have to prove competence once you get that bit if paper showing you have done training. From then on you are an expert.

    Yes and I have heaps of those bits of paper so everyone should call me Professor RC, still pretty incompetent though.
    Gold, the colour of choice for the discerning person.

  12. #12
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    Hi Guys,

    Whilst I understand the need for testing, I very much feel that it has become a bandwagon upon which firms jump to make money ! The ignorance of the people requiring equipment testing is readily taken advantage of by complex and misleading paperwork. I too did a "PAT" testing/training course and found very much as you describe, training from a script ! Where the trainer had very little knowledge or experience but simply someone given a job, a title and minimum pay so that their employer could make a large profit.

    I would venture to suggest that either a dedicated well trained, experienced in house engineer would be a better option or an individual that is skilled and knows what they are doing. Anyone can go out and purchase a tester and paper forms, use it without any understanding and fill in a form ! It makes a mockery of the whole purpose of testing.
    Best Regards:
    Baron J.

  13. #13
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    Yep, companies are just cashing-in on the government mandated testing requirements. I'm OK with that provided it's a small business who gives good customer service. What's happening in Oz is these small businesses get bought up by larger companies who then control the market. They also employ people with little to no experience on crappy conditions. Hence you get people like the incompetent, angry manager at the place I went to. Hopefully the mob racingtadpole recommended hasn't been corporatised yet.
    Chris

  14. #14
    BobL is online now Member: Blue and white apron brigade
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    One of the Uni faculties deemed their techos too valuable to be put on T&T duties just to be testing thousands of kettle cords every year., so they opted to simply replace all them every year - it was the cheapest way - especially as they could be bought for cents in bulk. You see there's no requirement to test any that are <12 months old. As a result there was for a while a small skips worth of the old ones up for grabs but so many disappeared they had to make them inaccessible. Sheer Maddness.

  15. #15
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    Slightly off the main topic of the thread, but in line with where it seems to be heading.

    I was employed by a religious organisation with interest in nursing homes, disability services, schools and residences for kids with multiple disabilities and syndromes, and early intervention services for about about 10 years. I was employed in a tech support role within the K12 school and residences for children with multiple disabilities, which was about 10% of the overall organisation. My role involved providing audio visual and computer development, production and support, maintenance and tech support for a wide range of disability aids within the school and children's residences. During this time, the whole T+T system was mandated and I was informed by the organisation's Chief Financial Officer that I would be given the responsibility of undertaking the T+T process for the entire organisation. Because of the enormity of the task and number of sites in the organisation, their history of taking every shortcut that admin could dream up, and then pushing staff under the bus if the foreseeable problems occurred, and the fact that I was a qualified electronics engineer, I declined to undertake the additional duty and responsibility being asked of me.

    They then dumped it upon one of the building maintenance/bus driver guys to do the job and he was required to present to head office to be trained/indoctrinated for the task before him, primarily concentrating on managing the internally developed documentation associated with it. The practical procedure he was instructed to undertake was to disconnect any and every mains powered item in every room of every building on every site, then reconnect it via a RCD equipped power board and turn the device on. If the device did not trip out the RCD on the power board, he was to document the item in his paperwork, sign and date a tag and apply to the power cord of the device, reconnect as found, and repeat for the next item etc. No inspection for faulty cables, no tagging of the actual devices if they had detachable power cables that could be operating something else the next day, and a whole raft of issues that meant the whole program was extremely dubious. I personally refused to take on the role because of potential personal liability issues that could arise in the event that something occurred to injure a client, and the signature trail led directly back to me, a qualified engineer who should be expected to know better.

    There came a time when this guy started working through the school and afterwards a range of anomalies and problems were noted. File servers dropped off line as he unplugged them to plug in his RCB power board, scrambling a lot of student documentation that had been accumulated over the years, and a whole range of battery only equipment sported T+T labels despite the fact that they could not have been tested either by the organisation's simple method, or by following the formal procedure that was implemented by the legislation. When I mentioned this to to the guy, he said he was instructed that everything electrical or electronic in every room had to be tagged and documented before he could leave the room, so if he couldn't test it according to the simple procedure he was given, he was to to tag it and include it in his documentation.

    I don't know if the situation improved after I left the next year, but I do know that they have had a number of issues with their care standards in nursing homes while I worked in the school, which continued to arise sporadically.
    I used to be an engineer, I'm not an engineer any more, but on the really good days I can remember when I was.

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